Apparatus for automatically filling well conduit strings



Sept. 13, 195 A. R. KOLSKY 2,717,649

APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUIT STRINGS Filed April 27, 1955 2 Sheets-Sheet l fak- INVENT pLEXQ/VQZF R 5X V pt- 13, 1955 A. R. KOLSKY 2,717,649

APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUIT STRINGS Filed April 27, 1953 2 Sheets-Sheet 2 5 i 4% 31 1 1- l 1 a! Z9 l 55 .5; 5/ L 3% a: A 11L i z i 7 if INVENTOR. E6. 4. mam/052 e, w; 5%

Uited States Patent APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUIT STRINGS Alexander R. Kolsiry, Huntington Park, Calitl, assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application April 27, 1953, Seriai No. 351,407

12 Claims. (Cl. 166-225) The present invention relates to subsurface well apparatus, and more particularly to apparatus for filling a string of well casing, drill pipe, or the like, with fluid in the well bore as it is lowered therewithin.

In strings of oil and gas well casing, and similar conduit strings, to be disposed in the well bore, it is usual practice to provide a back pressure valve to preclude return flow of fluids, such as cement slurry, into the casing string after it has been ejected therefrom. The presence of the back pressure valve also prevents the well bore fluid from entering the casing string while the latter is being lowered in the well bore, necessitating filling of the casing string from the top of the hole, which is a time consuming operation.

Accordingly, it is an object of the present invention to provide improved back pressure valve apparatus to be incorporated in a conduit string, which allows upward flow of the well bore fluid in the conduit string as it is being lowered in the well bore by holding the back pressure valve in an ineflective position, the valve later being rendered effective to prevent upward fluid flow in the conduit string. The valve is held in ineffective position in such manner as to minimize erosive wear upon it by the fluid flowing in the conduit string, assuring proper closing of the valve when it is rendered effective.

Another object of the invention is to provide apparatus of the character indicated that enables the conduit string to fill with the well bore fluid, in which the back pressure valve member, that may be in the form of a sphere or ball, is free to occupy a multiplicity of positions in engagement with a companion valve seat, thereby assuring leakproof contact therewith. In a more limited sense, the ball, or equivalent, back pressure valve member has an uninterrupted surface, being free to shift into any position in the apparatus and still engage its companion seat in leakproof fashion.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a longitudinal section through one form of apparatus, with the parts in the position they occupy while the apparatus is being lowered in the Well bore;

Fig. 2 is a cross-section taken along the line 2-2 on Fig. 1;

Fig. 3 is a cross-section taken along the line 3--3 on Fig. 1;

Fig. 4 is a view similar to Fig. 1, disclosing the filling valve mechanism in closed position;

Fig. 5 is a view similar to Fig. l, disclosing the auto- 2,717,549 Patented Sept. 13, 1955 matic valve mechanism disposed in an ineffective or inoperative position.

As disclosed in the drawings, the apparatus is provided within a casing shoe A adapted to form the lower end of a string of well casing B, or the like, disposed in a well bore. It is to be understood, however, that the apparatus could be incorporated at any desired upper point in the casing string.

As disclosed, the apparatus includes an outer tubular member having an upper threaded box 11 threadedly secured .on the lower end of an adjoining upper section of well casing B. The tubular member is provided with a plurality of longitudinally spaced circumferential internal grooves 12 adapted to receive the external ribs 13 of a cementitious plug 14 cast in the tubular member. The lower end 15 of this plug is rounded, to provide a guiding nose for the purpose of steering the casing past restrictions or obstructions encountered in the well bore while the casing string B is being lowered therewithin.

The apparatus has a central passage 16 therethrough which also extends completely through the cementitious plug 14. The latter has a back pressure valve device 17 in its lower portion, which can prevent upward flow of fluid through the passage 16 when allowed to function. This back pressure valve device includes a tubular stop member 18 in the cementitious plug having a plurality of circumferentially spaced lugs or fingers 19 upon which a back pressure valve element 20, in the form of a ball can rest. When engaged with the stop lugs or fingers 19, the ball 20 is disposed downwardly by a substantial distance away from a companion valve seat 21 secured in the cement plug 14. In order to preclude leakage between the valve seat 21 and the ball 20, a seal ring 22, adapted to be engaged by the ball, is clamped between the seat 21 and a retainer ring 23, the lower end of the latter engaging the upper end of the tubular stop member 18.

When the ball valve element 20 is allowed to move upwardly into engagement with its seat 21, fluid in the well bore cannot flow upwardly into the casing string B. During lowering of the casing string through the fluid in the well bore, it is desired to prevent the back pressure valve element 20 from engaging its seat 21, so as to allow the well casing B to fill automatically with the well bore fluid. An automatic casing filling valve device is provided in the shoe above the back pressure valve member 20, this device not only allowing the well casing to fill with the well bore fluid, but also holding the ball valve element from engagement with its seat 21.

As shown in the drawings, the automatic casing filling valve device includes a tubular housing 24 which is secured to the cementitious plug 14, as by providing external grooves 25 in the housing receiving the cement plug ribs 26. As shown in the drawings, and for convenience of assembly, the housing is made in three sections, including a lower section 27 engaging the upper end of the valve seat 21, an intermediate section 28, and an upper section 29 having its lower portion piloted within the intermediate section.

The intermediate section 28 initially supports the valve mechanism for preventing the ball valve member 20 from engaging its seat 21. This mechanism includes a central rod or stem 30, the lower end of which engages the ball member 20 and maintains it downwardly from engagement with its seat 21. The ball member 20 may, however, be free to rotate or move Within the tubular stop member 18. The rod or stem 30 extends completely through a tubular annular valve seat member 31. This latter member includes a sleeve or rod portion 32 and an upper seat portion 33 having an upwardly and inwardly tapered frusto-conical seating surface 34 adapted to be engaged by a companion seating edge 35 of a tubular valve member 36 slidable in the upper housing section or portion 29. The sleeve portion 32 of the annular valve seat member is releasably secured to the rod or stem 30, as by means of a shear pin 37 extending transversely through both of the members. The sleeve portion also extends through the hub portion 38 of a spider 39 integral with the intermediate housing section 28. This hub portion is attached to the outer wall of the intermediate section by a plurality of circumferentially spaced radial ribs 40, the circumferential spaces 41 between the ribs allowing passage area for fluid to flow through the spider 39.

The sleeve portion 32 of the valve seat is initially and releasably secured to the spider hub 38 by a plurality of frangible elements in the form of shear pins 42 extending radially through the hub and into the sleeve. These pins are prevented from moving in an outward direction by an encompassing retainer sleeve 43 which is prevented from dropping down along the hub 32 by a screw 44 threaded into the hub and engaging the lower end of the retainer member 43.

It is apparent that when the shear pins 37, 42 are intact, the rod 30 is held in a downward direction, to prevent upward movement of the ball valve member 20 into engagement with its companion seat 21. During lowering of the casing string B in the well bore C, the fluid disposed in the latter can flow upwardly into the lower end of the passage 16, between the stop lugs or firigers 19, around the ball valve member 20, through the valve seat 21 and on upwardly through the tubular housing 24. The fluid may also flow upwardly around the valve seat 31 when the tubular valve member 36 is in its upward position, proceeding upwardly through the latter and into the casing sections B thereabove. In the form of device disclosed in the drawings, when the fluid level in the well casing B reaches a predetermined height with respect to the external fluid level, then the tubular valve member 36 can shift downwardly into engagement with the valve seat 31 and preclude any further upward passage of fluid between the seat 31 and the valve member 36.

The tubular valve member 36 includes an upper large diameter portion 45 slidably engaging a cylindrical wall 46 in the upper housing section 29. The valve member 36 also includes a lower portion 47 having a smaller external diameter than the upper portion 45 and slidably engaging a lower cylindrical wall 48 of the upper housing section, which has an inside diameter that is less than the inside diameter of the upper cylindrical wall 46. Leakage between the tubular member 36 and its cylindrical walls is prevented by providing a plurality of side seal rings 49, such as rubber-like 0 rings, in ring grooves 50 in the tubular member, which sealingly engage the cylindrical walls 46, 48. These rings preclude the well bore fluid from entering the annular space 51 defined between the upper and lower tubular member portions 45, 47 and the cylindrical walls 46, 48. It is to be noted that the upper portion 45 has a lower shoulder 52 adapted to engage a companion lower shoulder 53 formed between the upper and lower cylindrical walls 46, 48 of the housing, in order to limit the extent of downward movement of the tubular valve member 36 in the upper housing section 29. Upward movement of the tubular valve member 36 is limited by its engagement with a split retainer ring 54 disposed within a groove 55 in the upper portion of the upper housing section 29.

As stated above, the well bore fluid, as well as the fluid within the casing string, is prevented from entering the confined space 51 between the upper and lower tubular valve member portions 45, 47. Since the smaller cylinder 48 has a lesser diameter than the larger cylinder 46, and the lower portion 47 of valve member has a correspondingly lesser diameter than that of the upper portion 45 of the valve member, the downwardly facing area R of the valve member 36 over which fluid can act to urge the valve in an upward direction is substantially less than the upwardly facing area S over which the fluid above the valve member can act. Thus, the annular area R between the inner wall 56 of the valve member and the smaller diameter cylinder wall 48 is less than the annular area S between the inner wall 56 of the valve member 36 and the larger diameter cylinder wall 46. Accordingly, fluid under pressure below the valve member 36, which corresponds to the hydrostatic head of fluid externally of the casing string B, is acting over the area R to urge the valve member 36 in an upward direction out of engagement from its-companion seat 31. The pressure of the fluid within the casing string B, which corresponds to the hydrostatic head of fluid therewithin, is acting in a downward direction over the area S of the valve member 36, tending to urge the latter in a downward direction into engagement with the valve seat 31. A balanced condition on the valve will be realized when the pressure acting upwardly on the valve member over the area R is equal to the pressure acting on the valve memher in the opposite direction over the area S. Since the area R is less than the area S, a balanced condition will be obtained when there is a lesser pressure internally of the casing string than exists externally thereof. Expressed by way of formula, a balanced condition will exist when:

P1R=P2S in which:

P1=the hydrostatic head of fluid externally of the well casing; and

1?z=the hydrostatic head of fluid internally of the well casing.

The hydrostatic heads of fluid externally and internally of the well casing will, therefore, be inversely proportional to the areas S and R. Since the area S is greater than the area R, the hydrostatic head of fluid internally of the well casing will be less than the hydrostatic head of fluid externally of the well casing. As the hydrostatic head of fluid within the well casing increases to a suflicient extent, it will shift the valve member 36 downwardly into engagement with the valve seat 31, preventing further upward passage of fluid into the well casing until the casing string has been lowered in the well bore fluid to a further extent.

When the hydrostatic head of fluid within the well casing has risen to a sufficient extent to shift the valve member 36 downwardly into engagement with its companion seat 31, fluid cannot move between the valve member and seat in either direction. Assurance is had that this fluid will not leak in an upward direction through other parts, as by providing a side seal 57, such as a rubber-like O ring, in a peripheral groove 58 in the rod or stem 30, which engages the wall 59 of the bore through the sleeve portion 32 of the annular valve seat member 31. This rod 30, as described above, is adapted to engage the ball back pressure valve element 20 to prevent its upward movement into contact with its companion seat 21 when the shear pins 37, 42 are intact. However, when the shear pin 37 is disrupted, it is desired to elevate the rod 30 to a position in which it is out of engagement with the ball valve member 20, despite the fact that the latter has moved upwardly into engagement with its companion seat 21. To accomplish this objective, a helical compression spring 60 is disposed around the upper portion of the rod 30, bearing upon an upper flange or spring seat 61 provided on the rod, the lower end of the spring engaging a shoulder 62 provided by a counterbore 63 in the valve seat member 31. When the shear pin 37 is disrupted, the spring 60 will expand, to elevate the rod 30 to a substantial extent well above the ball valve element 20. I

The apparatus A, B is run in the well bore C with the shear pins 37, 42 intact and the rod or stem 30 holding the back pressure valve element 20 in a downward position out of engagement from its valve seat 21. The valve element 20, however, is not necessarily held firmly against the stop lugs or fingers 19. It is preferred that the valve element be free to rotate. Accordingly, while the Well casing B is being lowered through the fluid in the well bore C, the fluid can pass upwardly around the ball valve members and may rotate it to different positions, thereby minimizing erosive wear on the ball valve member. The fluid will flow upwardly around the ball valve member 20 and on into the tubular housing 24. It will act upon the lower end of the tubular valve member 36 and shift the latter in an upward direction out of engagement from its companion seat 31, the fluid then flowing into the tubular valve member 36 and on into the well casing sections B thereabove (Fig. 1).

As the fluid level in the well casing B rises, the hydrostatic head of fluid is acting in a downward direction over the upper end. of the tubular valve member 36, and when this fluid level reaches a predetermined height compared to the external fluid level the tubular or sleeve 5 valve member 36 will be shifted downwardly into engagement with its companion seat 31, thereby precluding any further upward flow of fluid into the well casing B. The closed condition of the differential valve device is illustrated in Fig. 4, from which it will be noted that the valve member shoulder 52 is still spaced a substantial distance above the companion stop shoulder 36 in the upper housing section 29.

As added sections of well casing B are provided at the top of the hole and the casing string lowered to further extents through the fluid in the well bore, the tubular valve member 36 will be shifted between the open position shown in Fig. 1 and the closed position shown in Fig. 4, allowing the well casing to fill with fluid to its predetermined height relative to the height of the fluid externally of the casing string. After the casing has been run in the well bore to the. desired depth, the back pressure valve element 20 should be rendered operative. To perform this action, the well casing string B is completely filled with fluid through its upper portion, whereupon a pressure of a sufficient value is imposed on the fluid in the casing string. This pressure acts in a downward direction over the tubular valve member 36 and also over the valve seat 31, shearing the pins 37, 42 securing the valve seat 31 to the rod 30, and also securing the valve seat to the hub 38 of the spider 39. When the hub pins 42 are sheared, the valve seat 31 can drop downwardly until its upper portion 33 rests upon the upper end of the hub 38 (Fig. 5). The rod pin 37 will also be sheared, since it cannot move downwardly by virtue of its engagement with the ball valve member 20 and the support of the latter by the lugs or fingers 19.

When the rod pin 37 is sheared, the spring 60 is allowed to expand and elevate the rod to a substantial extent well above the ball valve member 20, as shown in Fig. 5, which then places the ball valve member in a position in which it can move upwardly into engagement with its companion seat 21, in the event that upward flow of fluid through the casing string B tends to occur. The valve seat member 31 will shift downwardly to the extent shown in Fig. 5, but the tubular valve member 36 can only move down to a slight extent until its shoulder 52 engages the companion stop 53 in the housing 24. 7 Accordingly, there is a substantial space between the valve member 36 and the valve seat 31 through which fluid can be pumped in a downward direction through the mechanism, for continued downward passage through the housing 24 and around the ball valve member 20, for discharge through the lower end of the shoe A. Cement slurry, or other fluids can be pumped down through the casing string B, passing down through the shoe A, to be ejected therefrom. When the pressure in the well casing is relieved, any tendency for the cement slurry to flow back into the casing string isprevented by the upward movement of the ball valve member 20 into engagement with its companion seat 21.

The provision of the large and small diameter valve portions 45, 47 enables the well casing to be lowered through the fluid in the well bore and prevents the fluid level in the casing string B from rising to too great an extent and overflowing at the top of the hole. However, the areas R and S could be madeequal, if desired, and, for that matter, equality would be produced, as a practical matter, by omitting the seal rings 49 from the tubular valve member. Should this type of device be used, then the fluid level in the well casing would rise to equality with the external fluid level, and the device would then function to prevent the back pressure valve element 20 from engaging its seat until desired.

With the arrangement described, the ball valve element 20 is free to shift in all directions during lowering of the apparatus in the well bore. Accordingly, no concentrated erosive wear occurs on the ball valve element which might be caused by the well fluid flowing thereby. The ball valve element can rotate to any position, having three degrees of freedom of movement. Similarly, when fluid is being pumped down the casing string, such as the cement slurry or circulating fluid used in conditioning the well bore, the ball valve element 20 is free to partake of universal movement on its stop lugs 19, thereby minimizing the tendency for the fluid to erode or cut the ball valve member. Accordingly, the ball valve member will remain as an uninterrupted spherical part, which, when moved upwardly into engagement with a companion seat 21, will provide a leakproof seal thereagainst. Accordingly, leakage of cement slurry, or other fluent substances, back into the casing string is prevented.

The inventor claims: 1

1. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; back pressure valve means in said tubular member to prevent upward flow of fluid therethrough; a valve device in said tubular member above said back pressure valve means including a valve member movable upwardly within said tubular member to open position to allow upward flow of fluid in said tubular member and movable downwardly within said tubular member to closed position to prevent downward flow of fluid in said tubular member; holding means releasably secured to said valve device and engaging said back pres sure valve means to prevent said back pressure valve means from closing while said valve member is moving between open and closed positions; and means for moving said holding means upwardly out of engagement from said back pressure valve means when said holding means is released from said valve device.

. 2. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be positioned in a well bore; a valve seat in said tubular member; a ball movable upwardly into engagement with said seat; a. valve device in said tubular member above said valve seat including a valve member movable upwardly within said tubular member to open position to allow upward flow of fluid into said tubular member and movable downwardly within said tubular member to closed position to prevent downward flow of fluid in said tubular member; holding means rcleasably secured to said valve device and engaging said ball to hold said ball downwardly away from said seat while said valve member is moving between open and closed positions; and means for moving said holding m-eans upwardly out of engagement from said ball when said holding means is released, to allow said ball to engage said seat.

3. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be positioned in a well bore; a valve seat in said tubular member; a ball movable upwardly into engagement'with' said seat; a valve device in said tubular member above said valve seat to allow upward flow of fluid in said tubular member and to restrict downward flow of fluid in said tubular member; a rod depending from said valve device; means releasably securing said rod to said valve device and in position to engage said ball and prevent said ball from engaging its seat; and means for moving said rod upwardly out of engagement from said ball when said releasable securing means is released to allow said ball to engage said seat.

4. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; back pressure valve means in said tubular member to prevent upward flow of fiuid therethrough; a valve device in said tubular member above said back pressure valve means to allow upward flow of fluid in said tubular member and to restrict downward flow of fluid in said tubular member; holding means releasably secured to said valve device and engaging said back pressure valve means to prevent said back pressure valve means from closing; and spring means engaging said holding means and valve device for moving said holding means upwardly out of engagement from said back pressure valve means when said holding means is released from said valve device.

5. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; back pressure valve means in. said tubular member to prevent upward flow of fluid therethrough; a valve device in said tubular member above said back pressure valve means to allow upward How of fluid in said tubular member and to restrict downward flow of fluid in said tubular member; a rod depending fromsaid valve device; means releasably securing said rod to said valve device and in position to engage said back pressure valve means and prevent said back pressure valve means from closing; and means for rnoving said rod upwardly out of engagement from said back pressure valve means when said releasable securing means is released to allow said back pressure valve means to close.

6. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; back pressure valve means in said tubular member to prevent upward flow of fluid therethrough; a valve seat in said tubular member above said back pressure valve means; a valve member movable downwardly into engagement with said seat; holding means depending from said seat; means releasably securing said holding means to said seat and in position to engage said back pressure valve means to prevent closing of said back pressure valve means; and means for moving said holding means upwardly out of engagement from said back pressure valve means when said reasable securing means is released to allow said back pressure valve means to close.

7. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; back pressure valve means in said tubular member to prevent upward flow of fluid therethrough; a valve seat in said tubular member above said back pressure valve means; a valve member movable downwardly into engagement with said seat; holding means depending from said seat; means releasably securing said holding means to said seat and in position to engage said back pressure valve means to prevent closing of said back pressure valve means; means for moving said holding means upwardly out of engagement from said back pressure valve means when said releasable securing means is released to allow said back pressure valve means to close; second means releasably securing said seat to said tubular member; and means for limiting downward movement of said valve member in said tubular member after release of said second releasable means to allow said seat to move downwardly away from said valve member.

8. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; a lower valve seat in said tubular member; a ball movable upwardly into engagement with said seat; an upper valve seat in said tubular member above said lower valve seat; a valve member movable downwardly into engagement with said upper seat; a rod depending from said upper valve seat; means releasably securing said rod to said upper valve seat and in position to engage said ball and prevent said ball from engaging said lower seat; and means for moving said rod upwardly out of engagement from said ball when said releasable securing means is released to allow said ball to engage said lower seat.

9. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; a lower valve seat in said tubular member; a ball movable upwardly into engagelent with said seat; an upper valve seat in said tubular member above said lower valve seat; a valve member movable downwardly into engagement with said upper seat; a rod depending from said upper valve seat; means releasably securing said rod to said upper valve seat and in position to engage said ball and prevent said ball from engaging said lower seat; means for moving said rod upwardly out of engagement from said ball when said releasable securing means is released to allow said ball to engage said lower seat; second means releasably securing said upper seat to said tubular member; and means for limiting downward movement of said valve member in said tubular member after release of said second releasable means to allow said upper seat to move downwardly away from said valve member.

10. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; a lower valve seat in said tubular member; a ball in said tubular member movable upwardly into engagement with said seat; an upper valve seat in said tubular member above said lower valve seat; a valve member movable downwardly into engagement with said upper seat; a rod extending in said upper seat and projecting downwardly therefrom; frangible means releasably connecting said rod to said upper seat to hold said rod in position to engage said ball to prevent said ball from engaging said lower seat; means for moving said rod upwardly out of engagement from said ball when said frangible means is released to allow said ball to engage said lower seat; second frangible means releasably securing said upper seat to said tubular member; and means for limiting downward movement of said valve member in said tubular member after release of said second frangible means to allow said upper seat to move downwardly away from said valve member.

11. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; a lower valve seat in said tubular member; a ball movable upwardly into engagement with said seat; an upper valve seat in said tubular member above said lower valve seat; a valve member movable downwardly into engagement with said upper seat; a rod depending from said upper seat; means releasably securing said rod to said upper valve seat and in position to engage said ball and prevent said ball from engaging said lower seat; a spring engaging said rod and upper seat to move said rod outwardly out of engagement from said ball when said releasable securing means is released to allow said ball to engage said lower seat; second means releasably securing said upper seat to said tubular member; and means for limiting downward movement of said valve member in said tubular member after release of said second releasable means to allow said upper seat to move downwardly away from said valve member.

12. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be disposed in a well bore; a lower valve seat in said tubular member; a ball in said tubular member movable upwardly into engagement with said seat; an upper valve seat in said tubular member above said lower valve seat; a valve member movable downwardly into engagement with said upper seat; a rod extending in said upper seat and projecting downwardly therefrom; first frangible means releasably connecting said rod to said upper seat to hold said rod in position to engage said ball to prevent said ball from engaging said lower seat; a spring engaging said rod and upper seat for moving said rod upwardly out of engagement from said ball when said first frangible securing means is disrupted to allow said ball to engage said lower seat; second frangible means releasably securing said upper seat to said tubular member; and means for limiting downward movement of said valve member in said tubular member after release of said second frangible means to allow said upper seat to move downwardly away from said valve member.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,747 Henderson Oct. 15, 1940 2,249,172 Quintrell July 15, 1941 2,300,854 Allen et a1. Nov. 3, 1942 2,540,455 Penick Feb. 6, 1951 

